Historically, sensitive, low-frequency electric-field sensors have been large devices, employing pairs of widely separated antennae or probes coupled to high-impedance voltmeters. The size of the antenna scales with the wavelength of the electromagnetic wave length and small sensors based on electro-optic materials are only sensitive at higher frequencies. More recently, a number of antenna-less electro-optic sensors have been employed to detect electric fields. Although such systems may be more compact than antenna systems, they are insensitive at low frequencies (e.g., frequencies below 100 MHz).
Compact sensors capable of detecting small, low-frequency electric fields could be applied for low-distance detection of power lines and taking electroencephalograms (EEGs), among other uses. Sensors requiring low power are especially desirable for portable applications.